Dynamic Stiffness of Hydraulic Bushing with Multiple Internal Configurations

Abstract

Fluid filled bushings are commonly used in vehicle suspension and sub-frame systems due to their spectrally-varying and amplitude-dependent properties. Since the literature on this topic is sparse, a controlled laboratory prototype bushing is first designed, constructed, and instrumented. This device provides different internal combination of long and short flow passages and flow restriction elements. Experiments with sinusoidal displacement excitations are conducted on the prototype, and dynamic stiffness spectra along with fluid chamber pressure responses are measured. The frequencydependent properties of several commonly seen hydraulic bushing designs are experimentally studied and compared under two excitation amplitudes. Further, new linear time-invariant models with one long and one short flow passages (in parallel or series) are proposed along with the limiting cases. The analytical models are validated in frequency and time domains using transmitted force and chamber pressure measurements. The proposed formulation provides insights into various performance features.

Dynamic Analysis of Hydraulic Bushings with Measured Nonlinear Compliance Parameters

“…In previous work [4,5,6,7,8], linear model parameters have been established through a combination of direct calculation and empirical estimation. The static stiffness curve, constitutive equations, and fluid mechanics principles of fluid resistance (related to viscosity) produce most of the parameters, but others are heavily geometrically dependent, and must therefore be estimated given the specific materials and configuration of a particular bushing design.…”

“…The transfer function method captures only the global behavior of the device and may not yield any insight regarding amplitude dependent behavior. The use of reduced-order models [4,5,6,7,8,9,10] to analyze hydraulic bushings offers useful simulation results and improved insight into the physics of the device, though prior work on such models has largely been limited to linear system theory [4,5,6,7,8]. Limited effort has focused on adding a single nonlinear element to more precisely describe the physics of a design feature [9,10].…”

Design of Hydraulic Bushing and Vehicle Testing for Reducing the Judder Vibration

“…The resistance R i (q i ) of the fluid passage can be modeled nonlinearly using the same orifice model as Eq. (5) [5] . ∆ Where C d is the expansion coefficient, A i is the cross-sectional area of the fluid passage, and c R is the resistance coefficient.…”

Harmonic amplitude dependent dynamic stiffness of hydraulic bushings: Alternate nonlinear models and experimental validation

“…Hydraulic elastomeric devices are often employed in automotive powertrain and suspension systems because of their unique dynamic properties, leading to both vibration isolation and motion control [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. These properties are achieved by an internal fluid system working in tandem with the elastomeric structure of a bushing.…”

“…Despite some similarities with hydraulic engine mounts that have been extensively studied [1][2][3][4][5][6][7][8][9], the behavior of hydraulic bushings is quite different and merits its own in-depth studies [10][11][12][13][14][15][16][17][18]. Prior, though limited, investigations of these devices have largely focused on simpler transfer function type formulations based on the linear time-invariant (LTI) system theory [10][11][12][13][14][15][16]. For instance, Arzanpour and Golnaraghi [12] developed a reduced order linear system model for a hydraulic bushing which attempts to capture some aspects of the physics, such as fluid resistance, compliance, and inertance.…”